Actin-driven host nuclear migration facilitates powdery mildew infection in pea

The position of the nucleus within a cell is highly dynamic and changes frequently in response to internal and external stimuli. Proper nuclear positioning within a cell determines cell behaviour and fate and is regulated by the cytoskeleton which serves as a track along which this organelle moves.

Movement of the plant cell nucleus towards the site of fungal attack is observed during compatible and incompatible plant-fungal interactions but the reason behind this movement is poorly understood. In this study, we investigated the nuclear and cytoskeletal dynamics of pea cells infected with the adapted powdery mildew fungus Erysiphe pisi. We observed that the plant cell nucleus repositions itself near the fungal penetration site as early as 9 hours post inoculation (hpi) and closely associates with the infection structure (haustorium) that develops from the penetration peg at 24 hpi. Once the fungus transitions to the reproductive phase, the plant nucleus moves away from the penetration site. Interestingly, this nuclear movement is regulated by the actin cytoskeleton and not by microtubules. Disrupting the actin cytoskeleton using pharmacological inhibitors hindered plant nuclear movement and powdery mildew haustorial formation. In addition, unlike microtubules, actin filaments change their orientation upon fungal infection and become more polarized towards the site of fungal penetration. Our study highlights the critical role of actin-mediated plant nuclear movement and actin polarization in facilitating pea colonization by the powdery mildew fungus.

Full article: Sharma, A. and Chandran, D. Host nuclear repositioning and actin polarization towards the site of penetration precedes fungal ingress during compatible pea-powdery mildew interactions. Planta 256, 45 (2022). https://doi.org/10.1007/s00425-022-03959-3